text: /*-------------------------------------------------------------------------
   *
   * indexcmds.c
   *	  POSTGRES define and remove index code.
   *
   * Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   *
   * IDENTIFICATION
   *	  src/backend/commands/indexcmds.c
   *
   *-------------------------------------------------------------------------
   */
  
  #include "postgres.h"
  
  #include "access/genam.h"
  #include "access/heapam.h"
  #include "access/reloptions.h"
  #include "access/transam.h"
  #include "access/xact.h"
  #include "catalog/catalog.h"
  #include "catalog/heap.h"
  #include "catalog/index.h"
  #include "catalog/indexing.h"
  #include "catalog/pg_opclass.h"
  #include "catalog/pg_opfamily.h"
  #include "catalog/pg_tablespace.h"
  #include "commands/dbcommands.h"
  #include "commands/defrem.h"
  #include "commands/tablecmds.h"
  #include "commands/tablespace.h"
  #include "mb/pg_wchar.h"
  #include "miscadmin.h"
  #include "nodes/nodeFuncs.h"
  #include "optimizer/clauses.h"
  #include "optimizer/planner.h"
  #include "parser/parse_coerce.h"
  #include "parser/parse_func.h"
  #include "parser/parse_oper.h"
  #include "parser/parsetree.h"
  #include "storage/lmgr.h"
  #include "storage/proc.h"
  #include "storage/procarray.h"
  #include "utils/acl.h"
  #include "utils/builtins.h"
  #include "utils/fmgroids.h"
  #include "utils/inval.h"
  #include "utils/lsyscache.h"
  #include "utils/memutils.h"
  #include "utils/relcache.h"
  #include "utils/snapmgr.h"
  #include "utils/syscache.h"
  #include "utils/tqual.h"
  
  
  /* non-export function prototypes */
  static void CheckPredicate(Expr *predicate);
  static void ComputeIndexAttrs(IndexInfo *indexInfo,
  				  Oid *collationOidP,
  				  Oid *classOidP,
  				  int16 *colOptionP,
  				  List *attList,
  				  List *exclusionOpNames,
  				  Oid relId,
  				  char *accessMethodName, Oid accessMethodId,
  				  bool amcanorder,
  				  bool isconstraint);
  static Oid GetIndexOpClass(List *opclass, Oid attrType,
  				char *accessMethodName, Oid accessMethodId);
  static char *ChooseIndexNameAddition(List *colnames);
  
  
  /*
   * DefineIndex
   *		Creates a new index.
   *
   * 'heapRelation': the relation the index will apply to.
   * 'indexRelationName': the name for the new index, or NULL to indicate
   *		that a nonconflicting default name should be picked.
   * 'indexRelationId': normally InvalidOid, but during bootstrap can be
   *		nonzero to specify a preselected OID for the index.
   * 'accessMethodName': name of the AM to use.
   * 'tableSpaceName': name of the tablespace to create the index in.
   *		NULL specifies using the appropriate default.
   * 'attributeList': a list of IndexElem specifying columns and expressions
   *		to index on.
   * 'predicate': the partial-index condition, or NULL if none.
   * 'options': reloptions from WITH (in list-of-DefElem form).
   * 'exclusionOpNames': list of names of exclusion-constraint operators,
   *		or NIL if not an exclusion constraint.
   * 'unique': make the index enforce uniqueness.
   * 'primary': mark the index as a primary key in the catalogs.
   * 'isconstraint': index is for a PRIMARY KEY or UNIQUE constraint,
   *		so build a pg_constraint entry for it.
   * 'deferrable': constraint is DEFERRABLE.
   * 'initdeferred': constraint is INITIALLY DEFERRED.
   * 'is_alter_table': this is due to an ALTER rather than a CREATE operation.
   * 'check_rights': check for CREATE rights in the namespace.  (This should
   *		be true except when ALTER is deleting/recreating an index.)
   * 'skip_build': make the catalog entries but leave the index file empty;
   *		it will be filled later.
   * 'quiet': suppress the NOTICE chatter ordinarily provided for constraints.
   * 'concurrent': avoid blocking writers to the table while building.
   */
  void
  DefineIndex(RangeVar *heapRelation,
  			char *indexRelationName,
  			Oid indexRelationId,
  			char *accessMethodName,
  			char *tableSpaceName,
  			List *attributeList,
  			Expr *predicate,
  			List *options,
  			List *exclusionOpNames,
  			bool unique,
  			bool primary,
  			bool isconstraint,
  			bool deferrable,
  			bool initdeferred,
  			bool is_alter_table,
  			bool check_rights,
  			bool skip_build,
  			bool quiet,
  			bool concurrent)
  {
  	Oid		   *collationObjectId;
  	Oid		   *classObjectId;
  	Oid			accessMethodId;
  	Oid			relationId;
  	Oid			namespaceId;
  	Oid			tablespaceId;
  	List	   *indexColNames;
  	Relation	rel;
  	Relation	indexRelation;
  	HeapTuple	tuple;
  	Form_pg_am	accessMethodForm;
  	bool		amcanorder;
  	RegProcedure amoptions;
  	Datum		reloptions;
  	int16	   *coloptions;
  	IndexInfo  *indexInfo;
  	int			numberOfAttributes;
  	VirtualTransactionId *old_lockholders;
  	VirtualTransactionId *old_snapshots;
  	int			n_old_snapshots;
  	LockRelId	heaprelid;
  	LOCKTAG		heaplocktag;
  	Snapshot	snapshot;
  	Relation	pg_index;
  	HeapTuple	indexTuple;
  	Form_pg_index indexForm;
  	int			i;
  
  	/*
  	 * count attributes in index
  	 */
  	numberOfAttributes = list_length(attributeList);
  	if (numberOfAttributes <= 0)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  				 errmsg("must specify at least one column")));
  	if (numberOfAttributes > INDEX_MAX_KEYS)
  		ereport(ERROR,
  				(errcode(ERRCODE_TOO_MANY_COLUMNS),
  				 errmsg("cannot use more than %d columns in an index",
  						INDEX_MAX_KEYS)));
  
  	/*
  	 * Open heap relation, acquire a suitable lock on it, remember its OID
  	 *
  	 * Only SELECT ... FOR UPDATE/SHARE are allowed while doing a standard
  	 * index build; but for concurrent builds we allow INSERT/UPDATE/DELETE
  	 * (but not VACUUM).
  	 */
  	rel = heap_openrv(heapRelation,
  					  (concurrent ? ShareUpdateExclusiveLock : ShareLock));
  
  	relationId = RelationGetRelid(rel);
  	namespaceId = RelationGetNamespace(rel);
  
  	/* Note: during bootstrap may see uncataloged relation */
  	if (rel->rd_rel->relkind != RELKIND_RELATION &&
  		rel->rd_rel->relkind != RELKIND_UNCATALOGED)
  	{
  		if (rel->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
  
  			/*
  			 * Custom error message for FOREIGN TABLE since the term is close
  			 * to a regular table and can confuse the user.
  			 */
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("cannot create index on foreign table \"%s\"",
  							heapRelation->relname)));
  		else
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("\"%s\" is not a table",
  							heapRelation->relname)));
  	}
  
  	/*
  	 * Don't try to CREATE INDEX on temp tables of other backends.
  	 */
  	if (RELATION_IS_OTHER_TEMP(rel))
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot create indexes on temporary tables of other sessions")));
  
  	/*
  	 * Verify we (still) have CREATE rights in the rel's namespace.
  	 * (Presumably we did when the rel was created, but maybe not anymore.)
  	 * Skip check if caller doesn't want it.  Also skip check if
  	 * bootstrapping, since permissions machinery may not be working yet.
  	 */
  	if (check_rights && !IsBootstrapProcessingMode())
  	{
  		AclResult	aclresult;
  
  		aclresult = pg_namespace_aclcheck(namespaceId, GetUserId(),
  										  ACL_CREATE);
  		if (aclresult != ACLCHECK_OK)
  			aclcheck_error(aclresult, ACL_KIND_NAMESPACE,
  						   get_namespace_name(namespaceId));
  	}
  
  	/*
  	 * Select tablespace to use.  If not specified, use default tablespace
  	 * (which may in turn default to database's default).
  	 */
  	if (tableSpaceName)
  	{
  		tablespaceId = get_tablespace_oid(tableSpaceName, false);
  	}
  	else
  	{
  		tablespaceId = GetDefaultTablespace(rel->rd_rel->relpersistence);
  		/* note InvalidOid is OK in this case */
  	}
  
  	/* Check permissions except when using database's default */
  	if (OidIsValid(tablespaceId) && tablespaceId != MyDatabaseTableSpace)
  	{
  		AclResult	aclresult;
  
  		aclresult = pg_tablespace_aclcheck(tablespaceId, GetUserId(),
  										   ACL_CREATE);
  		if (aclresult != ACLCHECK_OK)
  			aclcheck_error(aclresult, ACL_KIND_TABLESPACE,
  						   get_tablespace_name(tablespaceId));
  	}
  
  	/*
  	 * Force shared indexes into the pg_global tablespace.	This is a bit of a
  	 * hack but seems simpler than marking them in the BKI commands.  On the
  	 * other hand, if it's not shared, don't allow it to be placed there.
  	 */
  	if (rel->rd_rel->relisshared)
  		tablespaceId = GLOBALTABLESPACE_OID;
  	else if (tablespaceId == GLOBALTABLESPACE_OID)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  				 errmsg("only shared relations can be placed in pg_global tablespace")));
  
  	/*
  	 * Choose the index column names.
  	 */
  	indexColNames = ChooseIndexColumnNames(attributeList);
  
  	/*
  	 * Select name for index if caller didn't specify
  	 */
  	if (indexRelationName == NULL)
  		indexRelationName = ChooseIndexName(RelationGetRelationName(rel),
  											namespaceId,
  											indexColNames,
  											exclusionOpNames,
  											primary,
  											isconstraint);
  
  	/*
  	 * look up the access method, verify it can handle the requested features
  	 */
  	tuple = SearchSysCache1(AMNAME, PointerGetDatum(accessMethodName));
  	if (!HeapTupleIsValid(tuple))
  	{
  		/*
  		 * Hack to provide more-or-less-transparent updating of old RTREE
  		 * indexes to GiST: if RTREE is requested and not found, use GIST.
  		 */
  		if (strcmp(accessMethodName, "rtree") == 0)
  		{
  			ereport(NOTICE,
  					(errmsg("substituting access method \"gist\" for obsolete method \"rtree\"")));
  			accessMethodName = "gist";
  			tuple = SearchSysCache1(AMNAME, PointerGetDatum(accessMethodName));
  		}
  
  		if (!HeapTupleIsValid(tuple))
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_OBJECT),
  					 errmsg("access method \"%s\" does not exist",
  							accessMethodName)));
  	}
  	accessMethodId = HeapTupleGetOid(tuple);
  	accessMethodForm = (Form_pg_am) GETSTRUCT(tuple);
  
  	if (unique && !accessMethodForm->amcanunique)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  			   errmsg("access method \"%s\" does not support unique indexes",
  					  accessMethodName)));
  	if (numberOfAttributes > 1 && !accessMethodForm->amcanmulticol)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  		  errmsg("access method \"%s\" does not support multicolumn indexes",
  				 accessMethodName)));
  	if (exclusionOpNames != NIL && !OidIsValid(accessMethodForm->amgettuple))
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  		errmsg("access method \"%s\" does not support exclusion constraints",
  			   accessMethodName)));
  
  	amcanorder = accessMethodForm->amcanorder;
  	amoptions = accessMethodForm->amoptions;
  
  	ReleaseSysCache(tuple);
  
  	/*
  	 * Validate predicate, if given
  	 */
  	if (predicate)
  		CheckPredicate(predicate);
  
  	/*
  	 * Parse AM-specific options, convert to text array form, validate.
  	 */
  	reloptions = transformRelOptions((Datum) 0, options, NULL, NULL, false, false);
  
  	(void) index_reloptions(amoptions, reloptions, true);
  
  	/*
  	 * Prepare arguments for index_create, primarily an IndexInfo structure.
  	 * Note that ii_Predicate must be in implicit-AND format.
  	 */
  	indexInfo = makeNode(IndexInfo);
  	indexInfo->ii_NumIndexAttrs = numberOfAttributes;
  	indexInfo->ii_Expressions = NIL;	/* for now */
  	indexInfo->ii_ExpressionsState = NIL;
  	indexInfo->ii_Predicate = make_ands_implicit(predicate);
  	indexInfo->ii_PredicateState = NIL;
  	indexInfo->ii_ExclusionOps = NULL;
  	indexInfo->ii_ExclusionProcs = NULL;
  	indexInfo->ii_ExclusionStrats = NULL;
  	indexInfo->ii_Unique = unique;
  	/* In a concurrent build, mark it not-ready-for-inserts */
  	indexInfo->ii_ReadyForInserts = !concurrent;
  	indexInfo->ii_Concurrent = concurrent;
  	indexInfo->ii_BrokenHotChain = false;
  
  	collationObjectId = (Oid *) palloc(numberOfAttributes * sizeof(Oid));
  	classObjectId = (Oid *) palloc(numberOfAttributes * sizeof(Oid));
  	coloptions = (int16 *) palloc(numberOfAttributes * sizeof(int16));
  	ComputeIndexAttrs(indexInfo, collationObjectId, classObjectId,
  					  coloptions, attributeList,
  					  exclusionOpNames, relationId,
  					  accessMethodName, accessMethodId,
  					  amcanorder, isconstraint);
  
  	/*
  	 * Extra checks when creating a PRIMARY KEY index.
  	 */
  	if (primary)
  		index_check_primary_key(rel, indexInfo, is_alter_table);
  
  	/*
  	 * Report index creation if appropriate (delay this till after most of the
  	 * error checks)
  	 */
  	if (isconstraint && !quiet)
  	{
  		const char *constraint_type;
  
  		if (primary)
  			constraint_type = "PRIMARY KEY";
  		else if (unique)
  			constraint_type = "UNIQUE";
  		else if (exclusionOpNames != NIL)
  			constraint_type = "EXCLUDE";
  		else
  		{
  			elog(ERROR, "unknown constraint type");
  			constraint_type = NULL;		/* keep compiler quiet */
  		}
  
  		ereport(NOTICE,
  		  (errmsg("%s %s will create implicit index \"%s\" for table \"%s\"",
  				  is_alter_table ? "ALTER TABLE / ADD" : "CREATE TABLE /",
  				  constraint_type,
  				  indexRelationName, RelationGetRelationName(rel))));
  	}
  
  	/*
  	 * Make the catalog entries for the index, including constraints. Then, if
  	 * not skip_build || concurrent, actually build the index.
  	 */
  	indexRelationId =
  		index_create(rel, indexRelationName, indexRelationId,
  					 indexInfo, indexColNames,
  					 accessMethodId, tablespaceId,
  					 collationObjectId, classObjectId,
  					 coloptions, reloptions, primary,
  					 isconstraint, deferrable, initdeferred,
  					 allowSystemTableMods,
  					 skip_build || concurrent,
  					 concurrent);
  
  	if (!concurrent)
  	{
  		/* Close the heap and we're done, in the non-concurrent case */
  		heap_close(rel, NoLock);
  		return;
  	}
  
  	/* save lockrelid and locktag for below, then close rel */
  	heaprelid = rel->rd_lockInfo.lockRelId;
  	SET_LOCKTAG_RELATION(heaplocktag, heaprelid.dbId, heaprelid.relId);
  	heap_close(rel, NoLock);
  
  	/*
  	 * For a concurrent build, it's important to make the catalog entries
  	 * visible to other transactions before we start to build the index. That
  	 * will prevent them from making incompatible HOT updates.	The new index
  	 * will be marked not indisready and not indisvalid, so that no one else
  	 * tries to either insert into it or use it for queries.
  	 *
  	 * We must commit our current transaction so that the index becomes
  	 * visible; then start another.  Note that all the data structures we just
  	 * built are lost in the commit.  The only data we keep past here are the
  	 * relation IDs.
  	 *
  	 * Before committing, get a session-level lock on the table, to ensure
  	 * that neither it nor the index can be dropped before we finish. This
  	 * cannot block, even if someone else is waiting for access, because we
  	 * already have the same lock within our transaction.
  	 *
  	 * Note: we don't currently bother with a session lock on the index,
  	 * because there are no operations that could change its state while we
  	 * hold lock on the parent table.  This might need to change later.
  	 */
  	LockRelationIdForSession(&heaprelid, ShareUpdateExclusiveLock);
  
  	PopActiveSnapshot();
  	CommitTransactionCommand();
  	StartTransactionCommand();
  
  	/*
  	 * Phase 2 of concurrent index build (see comments for validate_index()
  	 * for an overview of how this works)
  	 *
  	 * Now we must wait until no running transaction could have the table open
  	 * with the old list of indexes.  To do this, inquire which xacts
  	 * currently would conflict with ShareLock on the table -- ie, which ones
  	 * have a lock that permits writing the table.	Then wait for each of
  	 * these xacts to commit or abort.	Note we do not need to worry about
  	 * xacts that open the table for writing after this point; they will see
  	 * the new index when they open it.
  	 *
  	 * Note: the reason we use actual lock acquisition here, rather than just
  	 * checking the ProcArray and sleeping, is that deadlock is possible if
  	 * one of the transactions in question is blocked trying to acquire an
  	 * exclusive lock on our table.  The lock code will detect deadlock and
  	 * error out properly.
  	 *
  	 * Note: GetLockConflicts() never reports our own xid, hence we need not
  	 * check for that.	Also, prepared xacts are not reported, which is fine
  	 * since they certainly aren't going to do anything more.
  	 */
  	old_lockholders = GetLockConflicts(&heaplocktag, ShareLock);
  
  	while (VirtualTransactionIdIsValid(*old_lockholders))
  	{
  		VirtualXactLockTableWait(*old_lockholders);
  		old_lockholders++;
  	}
  
  	/*
  	 * At this moment we are sure that there are no transactions with the
  	 * table open for write that don't have this new index in their list of
  	 * indexes.  We have waited out all the existing transactions and any new
  	 * transaction will have the new index in its list, but the index is still
  	 * marked as "not-ready-for-inserts".  The index is consulted while
  	 * deciding HOT-safety though.	This arrangement ensures that no new HOT
  	 * chains can be created where the new tuple and the old tuple in the
  	 * chain have different index keys.
  	 *
  	 * We now take a new snapshot, and build the index using all tuples that
  	 * are visible in this snapshot.  We can be sure that any HOT updates to
  	 * these tuples will be compatible with the index, since any updates made
  	 * by transactions that didn't know about the index are now committed or
  	 * rolled back.  Thus, each visible tuple is either the end of its
  	 * HOT-chain or the extension of the chain is HOT-safe for this index.
  	 */
  
  	/* Open and lock the parent heap relation */
  	rel = heap_openrv(heapRelation, ShareUpdateExclusiveLock);
  
  	/* And the target index relation */
  	indexRelation = index_open(indexRelationId, RowExclusiveLock);
  
  	/* Set ActiveSnapshot since functions in the indexes may need it */
  	PushActiveSnapshot(GetTransactionSnapshot());
  
  	/* We have to re-build the IndexInfo struct, since it was lost in commit */
  	indexInfo = BuildIndexInfo(indexRelation);
  	Assert(!indexInfo->ii_ReadyForInserts);
  	indexInfo->ii_Concurrent = true;
  	indexInfo->ii_BrokenHotChain = false;
  
  	/* Now build the index */
  	index_build(rel, indexRelation, indexInfo, primary, false);
  
  	/* Close both the relations, but keep the locks */
  	heap_close(rel, NoLock);
  	index_close(indexRelation, NoLock);
  
  	/*
  	 * Update the pg_index row to mark the index as ready for inserts. Once we
  	 * commit this transaction, any new transactions that open the table must
  	 * insert new entries into the index for insertions and non-HOT updates.
  	 */
  	pg_index = heap_open(IndexRelationId, RowExclusiveLock);
  
  	indexTuple = SearchSysCacheCopy1(INDEXRELID,
  									 ObjectIdGetDatum(indexRelationId));
  	if (!HeapTupleIsValid(indexTuple))
  		elog(ERROR, "cache lookup failed for index %u", indexRelationId);
  	indexForm = (Form_pg_index) GETSTRUCT(indexTuple);
  
  	Assert(!indexForm->indisready);
  	Assert(!indexForm->indisvalid);
  
  	indexForm->indisready = true;
  
  	simple_heap_update(pg_index, &indexTuple->t_self, indexTuple);
  	CatalogUpdateIndexes(pg_index, indexTuple);
  
  	heap_close(pg_index, RowExclusiveLock);
  
  	/* we can do away with our snapshot */
  	PopActiveSnapshot();
  
  	/*
  	 * Commit this transaction to make the indisready update visible.
  	 */
  	CommitTransactionCommand();
  	StartTransactionCommand();
  
  	/*
  	 * Phase 3 of concurrent index build
  	 *
  	 * We once again wait until no transaction can have the table open with
  	 * the index marked as read-only for updates.
  	 */
  	old_lockholders = GetLockConflicts(&heaplocktag, ShareLock);
  
  	while (VirtualTransactionIdIsValid(*old_lockholders))
  	{
  		VirtualXactLockTableWait(*old_lockholders);
  		old_lockholders++;
  	}
  
  	/*
  	 * Now take the "reference snapshot" that will be used by validate_index()
  	 * to filter candidate tuples.	Beware!  There might still be snapshots in
  	 * use that treat some transaction as in-progress that our reference
  	 * snapshot treats as committed.  If such a recently-committed transaction
  	 * deleted tuples in the table, we will not include them in the index; yet
  	 * those transactions which see the deleting one as still-in-progress will
  	 * expect such tuples to be there once we mark the index as valid.
  	 *
  	 * We solve this by waiting for all endangered transactions to exit before
  	 * we mark the index as valid.
  	 *
  	 * We also set ActiveSnapshot to this snap, since functions in indexes may
  	 * need a snapshot.
  	 */
  	snapshot = RegisterSnapshot(GetTransactionSnapshot());
  	PushActiveSnapshot(snapshot);
  
  	/*
  	 * Scan the index and the heap, insert any missing index entries.
  	 */
  	validate_index(relationId, indexRelationId, snapshot);
  
  	/*
  	 * The index is now valid in the sense that it contains all currently
  	 * interesting tuples.	But since it might not contain tuples deleted just
  	 * before the reference snap was taken, we have to wait out any
  	 * transactions that might have older snapshots.  Obtain a list of VXIDs
  	 * of such transactions, and wait for them individually.
  	 *
  	 * We can exclude any running transactions that have xmin > the xmin of
  	 * our reference snapshot; their oldest snapshot must be newer than ours.
  	 * We can also exclude any transactions that have xmin = zero, since they
  	 * evidently have no live snapshot at all (and any one they might be in
  	 * process of taking is certainly newer than ours).  Transactions in other
  	 * DBs can be ignored too, since they'll never even be able to see this
  	 * index.
  	 *
  	 * We can also exclude autovacuum processes and processes running manual
  	 * lazy VACUUMs, because they won't be fazed by missing index entries
  	 * either.	(Manual ANALYZEs, however, can't be excluded because they
  	 * might be within transactions that are going to do arbitrary operations
  	 * later.)
  	 *
  	 * Also, GetCurrentVirtualXIDs never reports our own vxid, so we need not
  	 * check for that.
  	 *
  	 * If a process goes idle-in-transaction with xmin zero, we do not need to
  	 * wait for it anymore, per the above argument.  We do not have the
  	 * infrastructure right now to stop waiting if that happens, but we can at
  	 * least avoid the folly of waiting when it is idle at the time we would
  	 * begin to wait.  We do this by repeatedly rechecking the output of
  	 * GetCurrentVirtualXIDs.  If, during any iteration, a particular vxid
  	 * doesn't show up in the output, we know we can forget about it.
  	 */
  	old_snapshots = GetCurrentVirtualXIDs(snapshot->xmin, true, false,
  										  PROC_IS_AUTOVACUUM | PROC_IN_VACUUM,
  										  &n_old_snapshots);
  
  	for (i = 0; i < n_old_snapshots; i++)
  	{
  		if (!VirtualTransactionIdIsValid(old_snapshots[i]))
  			continue;			/* found uninteresting in previous cycle */
  
  		if (i > 0)
  		{
  			/* see if anything's changed ... */
  			VirtualTransactionId *newer_snapshots;
  			int			n_newer_snapshots;
  			int			j;
  			int			k;
  
  			newer_snapshots = GetCurrentVirtualXIDs(snapshot->xmin,
  													true, false,
  										 PROC_IS_AUTOVACUUM | PROC_IN_VACUUM,
  													&n_newer_snapshots);
  			for (j = i; j < n_old_snapshots; j++)
  			{
  				if (!VirtualTransactionIdIsValid(old_snapshots[j]))
  					continue;	/* found uninteresting in previous cycle */
  				for (k = 0; k < n_newer_snapshots; k++)
  				{
  					if (VirtualTransactionIdEquals(old_snapshots[j],
  												   newer_snapshots[k]))
  						break;
  				}
  				if (k >= n_newer_snapshots)		/* not there anymore */
  					SetInvalidVirtualTransactionId(old_snapshots[j]);
  			}
  			pfree(newer_snapshots);
  		}
  
  		if (VirtualTransactionIdIsValid(old_snapshots[i]))
  			VirtualXactLockTableWait(old_snapshots[i]);
  	}
  
  	/*
  	 * Index can now be marked valid -- update its pg_index entry
  	 */
  	pg_index = heap_open(IndexRelationId, RowExclusiveLock);
  
  	indexTuple = SearchSysCacheCopy1(INDEXRELID,
  									 ObjectIdGetDatum(indexRelationId));
  	if (!HeapTupleIsValid(indexTuple))
  		elog(ERROR, "cache lookup failed for index %u", indexRelationId);
  	indexForm = (Form_pg_index) GETSTRUCT(indexTuple);
  
  	Assert(indexForm->indisready);
  	Assert(!indexForm->indisvalid);
  
  	indexForm->indisvalid = true;
  
  	simple_heap_update(pg_index, &indexTuple->t_self, indexTuple);
  	CatalogUpdateIndexes(pg_index, indexTuple);
  
  	heap_close(pg_index, RowExclusiveLock);
  
  	/*
  	 * The pg_index update will cause backends (including this one) to update
  	 * relcache entries for the index itself, but we should also send a
  	 * relcache inval on the parent table to force replanning of cached plans.
  	 * Otherwise existing sessions might fail to use the new index where it
  	 * would be useful.  (Note that our earlier commits did not create reasons
  	 * to replan; relcache flush on the index itself was sufficient.)
  	 */
  	CacheInvalidateRelcacheByRelid(heaprelid.relId);
  
  	/* we can now do away with our active snapshot */
  	PopActiveSnapshot();
  
  	/* And we can remove the validating snapshot too */
  	UnregisterSnapshot(snapshot);
  
  	/*
  	 * Last thing to do is release the session-level lock on the parent table.
  	 */
  	UnlockRelationIdForSession(&heaprelid, ShareUpdateExclusiveLock);
  }
  
  
  /*
   * CheckMutability
   *		Test whether given expression is mutable
   */
  static bool
  CheckMutability(Expr *expr)
  {
  	/*
  	 * First run the expression through the planner.  This has a couple of
  	 * important consequences.	First, function default arguments will get
  	 * inserted, which may affect volatility (consider "default now()").
  	 * Second, inline-able functions will get inlined, which may allow us to
  	 * conclude that the function is really less volatile than it's marked. As
  	 * an example, polymorphic functions must be marked with the most volatile
  	 * behavior that they have for any input type, but once we inline the
  	 * function we may be able to conclude that it's not so volatile for the
  	 * particular input type we're dealing with.
  	 *
  	 * We assume here that expression_planner() won't scribble on its input.
  	 */
  	expr = expression_planner(expr);
  
  	/* Now we can search for non-immutable functions */
  	return contain_mutable_functions((Node *) expr);
  }
  
  
  /*
   * CheckPredicate
   *		Checks that the given partial-index predicate is valid.
   *
   * This used to also constrain the form of the predicate to forms that
   * indxpath.c could do something with.	However, that seems overly
   * restrictive.  One useful application of partial indexes is to apply
   * a UNIQUE constraint across a subset of a table, and in that scenario
   * any evaluatable predicate will work.  So accept any predicate here
   * (except ones requiring a plan), and let indxpath.c fend for itself.
   */
  static void
  CheckPredicate(Expr *predicate)
  {
  	/*
  	 * We don't currently support generation of an actual query plan for a
  	 * predicate, only simple scalar expressions; hence these restrictions.
  	 */
  	if (contain_subplans((Node *) predicate))
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot use subquery in index predicate")));
  	if (contain_agg_clause((Node *) predicate))
  		ereport(ERROR,
  				(errcode(ERRCODE_GROUPING_ERROR),
  				 errmsg("cannot use aggregate in index predicate")));
  
  	/*
  	 * A predicate using mutable functions is probably wrong, for the same
  	 * reasons that we don't allow an index expression to use one.
  	 */
  	if (CheckMutability(predicate))
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  		   errmsg("functions in index predicate must be marked IMMUTABLE")));
  }
  
  /*
   * Compute per-index-column information, including indexed column numbers
   * or index expressions, opclasses, and indoptions.
   */
  static void
  ComputeIndexAttrs(IndexInfo *indexInfo,
  				  Oid *collationOidP,
  				  Oid *classOidP,
  				  int16 *colOptionP,
  				  List *attList,	/* list of IndexElem's */
  				  List *exclusionOpNames,
  				  Oid relId,
  				  char *accessMethodName,
  				  Oid accessMethodId,
  				  bool amcanorder,
  				  bool isconstraint)
  {
  	ListCell   *nextExclOp;
  	ListCell   *lc;
  	int			attn;
  
  	/* Allocate space for exclusion operator info, if needed */
  	if (exclusionOpNames)
  	{
  		int			ncols = list_length(attList);
  
  		Assert(list_length(exclusionOpNames) == ncols);
  		indexInfo->ii_ExclusionOps = (Oid *) palloc(sizeof(Oid) * ncols);
  		indexInfo->ii_ExclusionProcs = (Oid *) palloc(sizeof(Oid) * ncols);
  		indexInfo->ii_ExclusionStrats = (uint16 *) palloc(sizeof(uint16) * ncols);
  		nextExclOp = list_head(exclusionOpNames);
  	}
  	else
  		nextExclOp = NULL;
  
  	/*
  	 * process attributeList
  	 */
  	attn = 0;
  	foreach(lc, attList)
  	{
  		IndexElem  *attribute = (IndexElem *) lfirst(lc);
  		Oid			atttype;
  		Oid			attcollation;
  
  		/*
  		 * Process the column-or-expression to be indexed.
  		 */
  		if (attribute->name != NULL)
  		{
  			/* Simple index attribute */
  			HeapTuple	atttuple;
  			Form_pg_attribute attform;
  
  			Assert(attribute->expr == NULL);
  			atttuple = SearchSysCacheAttName(relId, attribute->name);
  			if (!HeapTupleIsValid(atttuple))
  			{
  				/* difference in error message spellings is historical */
  				if (isconstraint)
  					ereport(ERROR,
  							(errcode(ERRCODE_UNDEFINED_COLUMN),
  						  errmsg("column \"%s\" named in key does not exist",
  								 attribute->name)));
  				else
  					ereport(ERROR,
  							(errcode(ERRCODE_UNDEFINED_COLUMN),
  							 errmsg("column \"%s\" does not exist",
  									attribute->name)));
  			}
  			attform = (Form_pg_attribute) GETSTRUCT(atttuple);
  			indexInfo->ii_KeyAttrNumbers[attn] = attform->attnum;
  			atttype = attform->atttypid;
  			attcollation = attform->attcollation;
  			ReleaseSysCache(atttuple);
  		}
  		else
  		{
  			/* Index expression */
  			Node	   *expr = attribute->expr;
  
  			Assert(expr != NULL);
  			atttype = exprType(expr);
  			attcollation = exprCollation(expr);
  
  			/*
  			 * Strip any top-level COLLATE clause.	This ensures that we treat
  			 * "x COLLATE y" and "(x COLLATE y)" alike.
  			 */
  			while (IsA(expr, CollateExpr))
  				expr = (Node *) ((CollateExpr *) expr)->arg;
  
  			if (IsA(expr, Var) &&
  				((Var *) expr)->varattno != InvalidAttrNumber)
  			{
  				/*
  				 * User wrote "(column)" or "(column COLLATE something)".
  				 * Treat it like simple attribute anyway.
  				 */
  				indexInfo->ii_KeyAttrNumbers[attn] = ((Var *) expr)->varattno;
  			}
  			else
  			{
  				indexInfo->ii_KeyAttrNumbers[attn] = 0; /* marks expression */
  				indexInfo->ii_Expressions = lappend(indexInfo->ii_Expressions,
  													expr);
  
  				/*
  				 * We don't currently support generation of an actual query
  				 * plan for an index expression, only simple scalar
  				 * expressions; hence these restrictions.
  				 */
  				if (contain_subplans(expr))
  					ereport(ERROR,
  							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("cannot use subquery in index expression")));
  				if (contain_agg_clause(expr))
  					ereport(ERROR,
  							(errcode(ERRCODE_GROUPING_ERROR),
  							 errmsg("cannot use aggregate function in index expression")));
  
  				/*
  				 * A expression using mutable functions is probably wrong,
  				 * since if you aren't going to get the same result for the
  				 * same data every time, it's not clear what the index entries
  				 * mean at all.
  				 */
  				if (CheckMutability((Expr *) expr))
  					ereport(ERROR,
  							(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  							 errmsg("functions in index expression must be marked IMMUTABLE")));
  			}
  		}
  
  		/*
  		 * Apply collation override if any
  		 */
  		if (attribute->collation)
  			attcollation = get_collation_oid(attribute->collation, false);
  
  		/*
  		 * Check we have a collation iff it's a collatable type.  The only
  		 * expected failures here are (1) COLLATE applied to a noncollatable
  		 * type, or (2) index expression had an unresolved collation.  But we
  		 * might as well code this to be a complete consistency check.
  		 */
  		if (type_is_collatable(atttype))
  		{
  			if (!OidIsValid(attcollation))
  				ereport(ERROR,
  						(errcode(ERRCODE_INDETERMINATE_COLLATION),
  						 errmsg("could not determine which collation to use for index expression"),
  						 errhint("Use the COLLATE clause to set the collation explicitly.")));
  		}
  		else
  		{
  			if (OidIsValid(attcollation))
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("collations are not supported by type %s",
  								format_type_be(atttype))));
  		}
  
  		collationOidP[attn] = attcollation;
  
  		/*
  		 * Identify the opclass to use.
  		 */
  		classOidP[attn] = GetIndexOpClass(attribute->opclass,
  										  atttype,
  										  accessMethodName,
  										  accessMethodId);
  
  		/*
  		 * Identify the exclusion operator, if any.
  		 */
  		if (nextExclOp)
  		{
  			List	   *opname = (List *) lfirst(nextExclOp);
  			Oid			opid;
  			Oid			opfamily;
  			int			strat;
  
  			/*
  			 * Find the operator --- it must accept the column datatype
  			 * without runtime coercion (but binary compatibility is OK)
  			 */
  			opid = compatible_oper_opid(opname, atttype, atttype, false);
  
  			/*
  			 * Only allow commutative operators to be used in exclusion
  			 * constraints. If X conflicts with Y, but Y does not conflict
  			 * with X, bad things will happen.
  			 */
  			if (get_commutator(opid) != opid)
  				ereport(ERROR,
  						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  						 errmsg("operator %s is not commutative",
  								format_operator(opid)),
  						 errdetail("Only commutative operators can be used in exclusion constraints.")));
  
  			/*
  			 * Operator must be a member of the right opfamily, too
  			 */
  			opfamily = get_opclass_family(classOidP[attn]);
  			strat = get_op_opfamily_strategy(opid, opfamily);
  			if (strat == 0)
  			{
  				HeapTuple	opftuple;
  				Form_pg_opfamily opfform;
  
  				/*
  				 * attribute->opclass might not explicitly name the opfamily,
  				 * so fetch the name of the selected opfamily for use in the
  				 * error message.
  				 */
  				opftuple = SearchSysCache1(OPFAMILYOID,
  										   ObjectIdGetDatum(opfamily));
  				if (!HeapTupleIsValid(opftuple))
  					elog(ERROR, "cache lookup failed for opfamily %u",
  						 opfamily);
  				opfform = (Form_pg_opfamily) GETSTRUCT(opftuple);
  
  				ereport(ERROR,
  						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  						 errmsg("operator %s is not a member of operator family \"%s\"",
  								format_operator(opid),
  								NameStr(opfform->opfname)),
  						 errdetail("The exclusion operator must be related to the index operator class for the constraint.")));
  			}
  
  			indexInfo->ii_ExclusionOps[attn] = opid;
  			indexInfo->ii_ExclusionProcs[attn] = get_opcode(opid);
  			indexInfo->ii_ExclusionStrats[attn] = strat;
  			nextExclOp = lnext(nextExclOp);
  		}
  
  		/*
  		 * Set up the per-column options (indoption field).  For now, this is
  		 * zero for any un-ordered index, while ordered indexes have DESC and
  		 * NULLS FIRST/LAST options.
  		 */
  		colOptionP[attn] = 0;
  		if (amcanorder)
  		{
  			/* default ordering is ASC */
  			if (attribute->ordering == SORTBY_DESC)
  				colOptionP[attn] |= INDOPTION_DESC;
  			/* default null ordering is LAST for ASC, FIRST for DESC */
  			if (attribute->nulls_ordering == SORTBY_NULLS_DEFAULT)
  			{
  				if (attribute->ordering == SORTBY_DESC)
  					colOptionP[attn] |= INDOPTION_NULLS_FIRST;
  			}
  			else if (attribute->nulls_ordering == SORTBY_NULLS_FIRST)
  				colOptionP[attn] |= INDOPTION_NULLS_FIRST;
  		}
  		else
  		{
  			/* index AM does not support ordering */
  			if (attribute->ordering != SORTBY_DEFAULT)
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("access method \"%s\" does not support ASC/DESC options",
  								accessMethodName)));
  			if (attribute->nulls_ordering != SORTBY_NULLS_DEFAULT)
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("access method \"%s\" does not support NULLS FIRST/LAST options",
  								accessMethodName)));
  		}
  
  		attn++;
  	}
  }
  
  /*
   * Resolve possibly-defaulted operator class specification
   */
  static Oid
  GetIndexOpClass(List *opclass, Oid attrType,
  				char *accessMethodName, Oid accessMethodId)
  {
  	char	   *schemaname;
  	char	   *opcname;
  	HeapTuple	tuple;
  	Oid			opClassId,
  				opInputType;
  
  	/*
  	 * Release 7.0 removed network_ops, timespan_ops, and datetime_ops, so we
  	 * ignore those opclass names so the default *_ops is used.  This can be
  	 * removed in some later release.  bjm 2000/02/07
  	 *
  	 * Release 7.1 removes lztext_ops, so suppress that too for a while.  tgl
  	 * 2000/07/30
  	 *
  	 * Release 7.2 renames timestamp_ops to timestamptz_ops, so suppress that
  	 * too for awhile.	I'm starting to think we need a better approach. tgl
  	 * 2000/10/01
  	 *
  	 * Release 8.0 removes bigbox_ops (which was dead code for a long while
  	 * anyway).  tgl 2003/11/11
  	 */
  	if (list_length(opclass) == 1)
  	{
  		char	   *claname = strVal(linitial(opclass));
  
  		if (strcmp(claname, "network_ops") == 0 ||
  			strcmp(claname, "timespan_ops") == 0 ||
  			strcmp(claname, "datetime_ops") == 0 ||
  			strcmp(claname, "lztext_ops") == 0 ||
  			strcmp(claname, "timestamp_ops") == 0 ||
  			strcmp(claname, "bigbox_ops") == 0)
  			opclass = NIL;
  	}
  
  	if (opclass == NIL)
  	{
  		/* no operator class specified, so find the default */
  		opClassId = GetDefaultOpClass(attrType, accessMethodId);
  		if (!OidIsValid(opClassId))
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_OBJECT),
  					 errmsg("data type %s has no default operator class for access method \"%s\"",
  							format_type_be(attrType), accessMethodName),
  					 errhint("You must specify an operator class for the index or define a default operator class for the data type.")));
  		return opClassId;
  	}
  
  	/*
  	 * Specific opclass name given, so look up the opclass.
  	 */
  
  	/* deconstruct the name list */
  	DeconstructQualifiedName(opclass, &schemaname, &opcname);
  
  	if (schemaname)
  	{
  		/* Look in specific schema only */
  		Oid			namespaceId;
  
  		namespaceId = LookupExplicitNamespace(schemaname);
  		tuple = SearchSysCache3(CLAAMNAMENSP,
  								ObjectIdGetDatum(accessMethodId),
  								PointerGetDatum(opcname),
  								ObjectIdGetDatum(namespaceId));
  	}
  	else
  	{
  		/* Unqualified opclass name, so search the search path */
  		opClassId = OpclassnameGetOpcid(accessMethodId, opcname);
  		if (!OidIsValid(opClassId))
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_OBJECT),
  					 errmsg("operator class \"%s\" does not exist for access method \"%s\"",
  							opcname, accessMethodName)));
  		tuple = SearchSysCache1(CLAOID, ObjectIdGetDatum(opClassId));
  	}
  
  	if (!HeapTupleIsValid(tuple))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("operator class \"%s\" does not exist for access method \"%s\"",
  						NameListToString(opclass), accessMethodName)));
  
  	/*
  	 * Verify that the index operator class accepts this datatype.	Note we
  	 * will accept binary compatibility.
  	 */
  	opClassId = HeapTupleGetOid(tuple);
  	opInputType = ((Form_pg_opclass) GETSTRUCT(tuple))->opcintype;
  
  	if (!IsBinaryCoercible(attrType, opInputType))
  		ereport(ERROR,
  				(errcode(ERRCODE_DATATYPE_MISMATCH),
  				 errmsg("operator class \"%s\" does not accept data type %s",
  					  NameListToString(opclass), format_type_be(attrType))));
  
  	ReleaseSysCache(tuple);
  
  	return opClassId;
  }
  
  /*
   * GetDefaultOpClass
   *
   * Given the OIDs of a datatype and an access method, find the default
   * operator class, if any.	Returns InvalidOid if there is none.
   */
  Oid
  GetDefaultOpClass(Oid type_id, Oid am_id)
  {
  	Oid			result = InvalidOid;
  	int			nexact = 0;
  	int			ncompatible = 0;
  	int			ncompatiblepreferred = 0;
  	Relation	rel;
  	ScanKeyData skey[1];
  	SysScanDesc scan;
  	HeapTuple	tup;
  	TYPCATEGORY tcategory;
  
  	/* If it's a domain, look at the base type instead */
  	type_id = getBaseType(type_id);
  
  	tcategory = TypeCategory(type_id);
  
  	/*
  	 * We scan through all the opclasses available for the access method,
  	 * looking for one that is marked default and matches the target type
  	 * (either exactly or binary-compatibly, but prefer an exact match).
  	 *
  	 * We could find more than one binary-compatible match.  If just one is
  	 * for a preferred type, use that one; otherwise we fail, forcing the user
  	 * to specify which one he wants.  (The preferred-type special case is a
  	 * kluge for varchar: it's binary-compatible to both text and bpchar, so
  	 * we need a tiebreaker.)  If we find more than one exact match, then
  	 * someone put bogus entries in pg_opclass.
  	 */
  	rel = heap_open(OperatorClassRelationId, AccessShareLock);
  
  	ScanKeyInit(&skey[0],
  				Anum_pg_opclass_opcmethod,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(am_id));
  
  	scan = systable_beginscan(rel, OpclassAmNameNspIndexId, true,
  							  SnapshotNow, 1, skey);
  
  	while (HeapTupleIsValid(tup = systable_getnext(scan)))
  	{
  		Form_pg_opclass opclass = (Form_pg_opclass) GETSTRUCT(tup);
  
  		/* ignore altogether if not a default opclass */
  		if (!opclass->opcdefault)
  			continue;
  		if (opclass->opcintype == type_id)
  		{
  			nexact++;
  			result = HeapTupleGetOid(tup);
  		}
  		else if (nexact == 0 &&
  				 IsBinaryCoercible(type_id, opclass->opcintype))
  		{
  			if (IsPreferredType(tcategory, opclass->opcintype))
  			{
  				ncompatiblepreferred++;
  				result = HeapTupleGetOid(tup);
  			}
  			else if (ncompatiblepreferred == 0)
  			{
  				ncompatible++;
  				result = HeapTupleGetOid(tup);
  			}
  		}
  	}
  
  	systable_endscan(scan);
  
  	heap_close(rel, AccessShareLock);
  
  	/* raise error if pg_opclass contains inconsistent data */
  	if (nexact > 1)
  		ereport(ERROR,
  				(errcode(ERRCODE_DUPLICATE_OBJECT),
  		errmsg("there are multiple default operator classes for data type %s",
  			   format_type_be(type_id))));
  
  	if (nexact == 1 ||
  		ncompatiblepreferred == 1 ||
  		(ncompatiblepreferred == 0 && ncompatible == 1))
  		return result;
  
  	return InvalidOid;
  }
  
  /*
   *	makeObjectName()
   *
   *	Create a name for an implicitly created index, sequence, constraint, etc.
   *
   *	The parameters are typically: the original table name, the original field
   *	name, and a "type" string (such as "seq" or "pkey").	The field name
   *	and/or type can be NULL if not relevant.
   *
   *	The result is a palloc'd string.
   *
   *	The basic result we want is "name1_name2_label", omitting "_name2" or
   *	"_label" when those parameters are NULL.  However, we must generate
   *	a name with less than NAMEDATALEN characters!  So, we truncate one or
   *	both names if necessary to make a short-enough string.	The label part
   *	is never truncated (so it had better be reasonably short).
   *
   *	The caller is responsible for checking uniqueness of the generated
   *	name and retrying as needed; retrying will be done by altering the
   *	"label" string (which is why we never truncate that part).
   */
  char *
  makeObjectName(const char *name1, const char *name2, const char *label)
  {
  	char	   *name;
  	int			overhead = 0;	/* chars needed for label and underscores */
  	int			availchars;		/* chars available for name(s) */
  	int			name1chars;		/* chars allocated to name1 */
  	int			name2chars;		/* chars allocated to name2 */
  	int			ndx;
  
  	name1chars = strlen(name1);
  	if (name2)
  	{
  		name2chars = strlen(name2);
  		overhead++;				/* allow for separating underscore */
  	}
  	else
  		name2chars = 0;
  	if (label)
  		overhead += strlen(label) + 1;
  
  	availchars = NAMEDATALEN - 1 - overhead;
  	Assert(availchars > 0);		/* else caller chose a bad label */
  
  	/*
  	 * If we must truncate,  preferentially truncate the longer name. This
  	 * logic could be expressed without a loop, but it's simple and obvious as
  	 * a loop.
  	 */
  	while (name1chars + name2chars > availchars)
  	{
  		if (name1chars > name2chars)
  			name1chars--;
  		else
  			name2chars--;
  	}
  
  	name1chars = pg_mbcliplen(name1, name1chars, name1chars);
  	if (name2)
  		name2chars = pg_mbcliplen(name2, name2chars, name2chars);
  
  	/* Now construct the string using the chosen lengths */
  	name = palloc(name1chars + name2chars + overhead + 1);
  	memcpy(name, name1, name1chars);
  	ndx = name1chars;
  	if (name2)
  	{
  		name[ndx++] = '_';
  		memcpy(name + ndx, name2, name2chars);
  		ndx += name2chars;
  	}
  	if (label)
  	{
  		name[ndx++] = '_';
  		strcpy(name + ndx, label);
  	}
  	else
  		name[ndx] = '\0';
  
  	return name;
  }
  
  /*
   * Select a nonconflicting name for a new relation.  This is ordinarily
   * used to choose index names (which is why it's here) but it can also
   * be used for sequences, or any autogenerated relation kind.
   *
   * name1, name2, and label are used the same way as for makeObjectName(),
   * except that the label can't be NULL; digits will be appended to the label
   * if needed to create a name that is unique within the specified namespace.
   *
   * Note: it is theoretically possible to get a collision anyway, if someone
   * else chooses the same name concurrently.  This is fairly unlikely to be
   * a problem in practice, especially if one is holding an exclusive lock on
   * the relation identified by name1.  However, if choosing multiple names
   * within a single command, you'd better create the new object and do
   * CommandCounterIncrement before choosing the next one!
   *
   * Returns a palloc'd string.
   */
  char *
  ChooseRelationName(const char *name1, const char *name2,
  				   const char *label, Oid namespaceid)
  {
  	int			pass = 0;
  	char	   *relname = NULL;
  	char		modlabel[NAMEDATALEN];
  
  	/* try the unmodified label first */
  	StrNCpy(modlabel, label, sizeof(modlabel));
  
  	for (;;)
  	{
  		relname = makeObjectName(name1, name2, modlabel);
  
  		if (!OidIsValid(get_relname_relid(relname, namespaceid)))
  			break;
  
  		/* found a conflict, so try a new name component */
  		pfree(relname);
  		snprintf(modlabel, sizeof(modlabel), "%s%d", label, ++pass);
  	}
  
  	return relname;
  }
  
  /*
   * Select the name to be used for an index.
   *
   * The argument list is pretty ad-hoc :-(
   */
  char *
  ChooseIndexName(const char *tabname, Oid namespaceId,
  				List *colnames, List *exclusionOpNames,
  				bool primary, bool isconstraint)
  {
  	char	   *indexname;
  
  	if (primary)
  	{
  		/* the primary key's name does not depend on the specific column(s) */
  		indexname = ChooseRelationName(tabname,
  									   NULL,
  									   "pkey",
  									   namespaceId);
  	}
  	else if (exclusionOpNames != NIL)
  	{
  		indexname = ChooseRelationName(tabname,
  									   ChooseIndexNameAddition(colnames),
  									   "excl",
  									   namespaceId);
  	}
  	else if (isconstraint)
  	{
  		indexname = ChooseRelationName(tabname,
  									   ChooseIndexNameAddition(colnames),
  									   "key",
  									   namespaceId);
  	}
  	else
  	{
  		indexname = ChooseRelationName(tabname,
  									   ChooseIndexNameAddition(colnames),
  									   "idx",
  									   namespaceId);
  	}
  
  	return indexname;
  }
  
  /*
   * Generate "name2" for a new index given the list of column names for it
   * (as produced by ChooseIndexColumnNames).  This will be passed to
   * ChooseRelationName along with the parent table name and a suitable label.
   *
   * We know that less than NAMEDATALEN characters will actually be used,
   * so we can truncate the result once we've generated that many.
   */
  static char *
  ChooseIndexNameAddition(List *colnames)
  {
  	char		buf[NAMEDATALEN * 2];
  	int			buflen = 0;
  	ListCell   *lc;
  
  	buf[0] = '\0';
  	foreach(lc, colnames)
  	{
  		const char *name = (const char *) lfirst(lc);
  
  		if (buflen > 0)
  			buf[buflen++] = '_';	/* insert _ between names */
  
  		/*
  		 * At this point we have buflen <= NAMEDATALEN.  name should be less
  		 * than NAMEDATALEN already, but use strlcpy for paranoia.
  		 */
  		strlcpy(buf + buflen, name, NAMEDATALEN);
  		buflen += strlen(buf + buflen);
  		if (buflen >= NAMEDATALEN)
  			break;
  	}
  	return pstrdup(buf);
  }
  
  /*
   * Select the actual names to be used for the columns of an index, given the
   * list of IndexElems for the columns.	This is mostly about ensuring the
   * names are unique so we don't get a conflicting-attribute-names error.
   *
   * Returns a List of plain strings (char *, not String nodes).
   */
  List *
  ChooseIndexColumnNames(List *indexElems)
  {
  	List	   *result = NIL;
  	ListCell   *lc;
  
  	foreach(lc, indexElems)
  	{
  		IndexElem  *ielem = (IndexElem *) lfirst(lc);
  		const char *origname;
  		const char *curname;
  		int			i;
  		char		buf[NAMEDATALEN];
  
  		/* Get the preliminary name from the IndexElem */
  		if (ielem->indexcolname)
  			origname = ielem->indexcolname;		/* caller-specified name */
  		else if (ielem->name)
  			origname = ielem->name;		/* simple column reference */
  		else
  			origname = "expr";	/* default name for expression */
  
  		/* If it conflicts with any previous column, tweak it */
  		curname = origname;
  		for (i = 1;; i++)
  		{
  			ListCell   *lc2;
  			char		nbuf[32];
  			int			nlen;
  
  			foreach(lc2, result)
  			{
  				if (strcmp(curname, (char *) lfirst(lc2)) == 0)
  					break;
  			}
  			if (lc2 == NULL)
  				break;			/* found nonconflicting name */
  
  			sprintf(nbuf, "%d", i);
  
  			/* Ensure generated names are shorter than NAMEDATALEN */
  			nlen = pg_mbcliplen(origname, strlen(origname),
  								NAMEDATALEN - 1 - strlen(nbuf));
  			memcpy(buf, origname, nlen);
  			strcpy(buf + nlen, nbuf);
  			curname = buf;
  		}
  
  		/* And attach to the result list */
  		result = lappend(result, pstrdup(curname));
  	}
  	return result;
  }
  
  /*
   * ReindexIndex
   *		Recreate a specific index.
   */
  void
  ReindexIndex(RangeVar *indexRelation)
  {
  	Oid			indOid;
  	HeapTuple	tuple;
  
  	indOid = RangeVarGetRelid(indexRelation, false);
  	tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(indOid));
  	if (!HeapTupleIsValid(tuple))		/* shouldn't happen */
  		elog(ERROR, "cache lookup failed for relation %u", indOid);
  
  	if (((Form_pg_class) GETSTRUCT(tuple))->relkind != RELKIND_INDEX)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not an index",
  						indexRelation->relname)));
  
  	/* Check permissions */
  	if (!pg_class_ownercheck(indOid, GetUserId()))
  		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
  					   indexRelation->relname);
  
  	ReleaseSysCache(tuple);
  
  	reindex_index(indOid, false);
  }
  
  /*
   * ReindexTable
   *		Recreate all indexes of a table (and of its toast table, if any)
   */
  void
  ReindexTable(RangeVar *relation)
  {
  	Oid			heapOid;
  	HeapTuple	tuple;
  
  	heapOid = RangeVarGetRelid(relation, false);
  	tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(heapOid));
  	if (!HeapTupleIsValid(tuple))		/* shouldn't happen */
  		elog(ERROR, "cache lookup failed for relation %u", heapOid);
  
  	if (((Form_pg_class) GETSTRUCT(tuple))->relkind != RELKIND_RELATION &&
  		((Form_pg_class) GETSTRUCT(tuple))->relkind != RELKIND_TOASTVALUE)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not a table",
  						relation->relname)));
  
  	/* Check permissions */
  	if (!pg_class_ownercheck(heapOid, GetUserId()))
  		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
  					   relation->relname);
  
  	ReleaseSysCache(tuple);
  
  	if (!reindex_relation(heapOid, REINDEX_REL_PROCESS_TOAST))
  		ereport(NOTICE,
  				(errmsg("table \"%s\" has no indexes",
  						relation->relname)));
  }
  
  /*
   * ReindexDatabase
   *		Recreate indexes of a database.
   *
   * To reduce the probability of deadlocks, each table is reindexed in a
   * separate transaction, so we can release the lock on it right away.
   * That means this must not be called within a user transaction block!
   */
  void
  ReindexDatabase(const char *databaseName, bool do_system, bool do_user)
  {
  	Relation	relationRelation;
  	HeapScanDesc scan;
  	HeapTuple	tuple;
  	MemoryContext private_context;
  	MemoryContext old;
  	List	   *relids = NIL;
  	ListCell   *l;
  
  	AssertArg(databaseName);
  
  	if (strcmp(databaseName, get_database_name(MyDatabaseId)) != 0)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("can only reindex the currently open database")));
  
  	if (!pg_database_ownercheck(MyDatabaseId, GetUserId()))
  		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_DATABASE,
  					   databaseName);
  
  	/*
  	 * Create a memory context that will survive forced transaction commits we
  	 * do below.  Since it is a child of PortalContext, it will go away
  	 * eventually even if we suffer an error; there's no need for special
  	 * abort cleanup logic.
  	 */
  	private_context = AllocSetContextCreate(PortalContext,
  											"ReindexDatabase",
  											ALLOCSET_DEFAULT_MINSIZE,
  											ALLOCSET_DEFAULT_INITSIZE,
  											ALLOCSET_DEFAULT_MAXSIZE);
  
  	/*
  	 * We always want to reindex pg_class first.  This ensures that if there
  	 * is any corruption in pg_class' indexes, they will be fixed before we
  	 * process any other tables.  This is critical because reindexing itself
  	 * will try to update pg_class.
  	 */
  	if (do_system)
  	{
  		old = MemoryContextSwitchTo(private_context);
  		relids = lappend_oid(relids, RelationRelationId);
  		MemoryContextSwitchTo(old);
  	}
  
  	/*
  	 * Scan pg_class to build a list of the relations we need to reindex.
  	 *
  	 * We only consider plain relations here (toast rels will be processed
  	 * indirectly by reindex_relation).
  	 */
  	relationRelation = heap_open(RelationRelationId, AccessShareLock);
  	scan = heap_beginscan(relationRelation, SnapshotNow, 0, NULL);
  	while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
  	{
  		Form_pg_class classtuple = (Form_pg_class) GETSTRUCT(tuple);
  
  		if (classtuple->relkind != RELKIND_RELATION)
  			continue;
  
  		/* Skip temp tables of other backends; we can't reindex them at all */
  		if (classtuple->relpersistence == RELPERSISTENCE_TEMP &&
  			!isTempNamespace(classtuple->relnamespace))
  			continue;
  
  		/* Check user/system classification, and optionally skip */
  		if (IsSystemClass(classtuple))
  		{
  			if (!do_system)
  				continue;
  		}
  		else
  		{
  			if (!do_user)
  				continue;
  		}
  
  		if (HeapTupleGetOid(tuple) == RelationRelationId)
  			continue;			/* got it already */
  
  		old = MemoryContextSwitchTo(private_context);
  		relids = lappend_oid(relids, HeapTupleGetOid(tuple));
  		MemoryContextSwitchTo(old);
  	}
  	heap_endscan(scan);
  	heap_close(relationRelation, AccessShareLock);
  
  	/* Now reindex each rel in a separate transaction */
  	PopActiveSnapshot();
  	CommitTransactionCommand();
  	foreach(l, relids)
  	{
  		Oid			relid = lfirst_oid(l);
  
  		StartTransactionCommand();
  		/* functions in indexes may want a snapshot set */
  		PushActiveSnapshot(GetTransactionSnapshot());
  		if (reindex_relation(relid, REINDEX_REL_PROCESS_TOAST))
  			ereport(NOTICE,
  					(errmsg("table \"%s.%s\" was reindexed",
  							get_namespace_name(get_rel_namespace(relid)),
  							get_rel_name(relid))));
  		PopActiveSnapshot();
  		CommitTransactionCommand();
  	}
  	StartTransactionCommand();
  
  	MemoryContextDelete(private_context);
  }
  